DESCRIPTION: This 4-year study is intended to (i) provide national prevalence data for the timing of sexual maturation of White, Black, and Mexican-American children in the US and examine secular changes since 1970, (ii) relate growth, including indices of obesity, to sexual maturity status, and (iii) derive adjustment factors for sexual maturity for application to US growth charts for stature, weight, and BMI. Existing sexual maturity and growth data from the national health surveys will be used. These surveys include: (i) The National Health Examination Survey Cycle II & III (NHES; 1963-1970), (ii) The Hispanic Health and Nutrition Examination Survey (HHANES; 1982-1984) , and (iii) The National Health and Nutrition Examination Survey (NHANES III; 1988-1994). The analyses will consider sample weights and effects of the complex survey design. There is a lack of current prevalence data for the timing of sexual maturity (secondary sex characteristics including age at menarche) for US children and for major ethnic subgroups. Such data will assist in the recognition of children with unusual rates of sexual maturation and numerous growth disorders including constitutional delay, hypothalamic pituitary hormone deficiencies, and primary gonadal failure. There has been a secular increase in the prevalence of overweight/obesity among US children, and obesity is clearly associated with early puberty. Ethnic differences in the prevalence of obesity are reported to be associated with the timing of sexual maturity, but no current information exists from recent US national health survey data. Adjustments for sexual maturity would "remove" the effects of variations in maturation rates from observed growth data. At present, it is not possible to account for sexual maturity on the US national growth charts or to evaluate effectively the growth of children with delayed or accelerated pubertal development. These adjustments will be applicable to children within normal variations in sexual maturation, e.g., within 3 standard deviations of the mean and are not intended for children with defined pathology affecting sexual maturation such as confirmed precocious puberty. The increased prevalence of obesity during pubescence may be associated with accelerated pubertal development. The prevention of teenage obesity would be well-served by taking sexual maturity into account when growth is assessed. The proposed investigation is timely, innovative and significant given the national concern regarding obesity and early maturation in US children.